Anatomy of a Marker
Markers (also called trackers) are the main tools you’ll use to track features in your footage, so before you start tracking, let’s understand what a marker is and what its parts do (see Figure 13.2).
Pattern area: This is the main part of the marker. The pattern is the area of the image in one frame that Blender (or you, manually) will look for in the next frame to track it. Usually, you should use some feature of the footage that is easy to recognize as the pattern’s center: a high-contrast area or a specific shape that is unique in the image. You can move the marker, rotate it, and scale it as always with G, R, and S. Also, in the Properties Region, in the Track panel, you’ll see an image that shows the selected marker’s pattern, so you can clearly see the pattern that Blender is analyzing.
Search area: This is the area in which Blender will look for the pattern defined in the pattern area in the next frame. (This area is not visible by default; you need to enable it in the Marker Display panel of the Properties Region if you want to see it.) The faster the movement of the image is, the bigger the search area will need to be, because if the pattern in the next frame falls outside of the search area, Blender won’t find it. However, the bigger the search area, the slower the automatic tracking will work. You can change the size of this area or its position by left clicking and dragging on its top-left and bottom-right marked corners.
Pattern orientation: You can rotate the pattern (or even distort it by dragging its corners) to make tracking it easier. If you do this, you also have options to track the pattern’s rotation or perspective, which can be very useful at times. In this example, though, you’ll only work with the markers’ locations. When you left click and drag the little square at the end of the short line, you’ll be able to rotate or scale the pattern (you can also do that using R and S when you select the marker).
Tracked frames: When you’re tracking, the marker will show a red and a blue line, both with dots. The track is always in the current frame’s position; the blue line shows the trajectory and positions of the next frames (if tracked) and the red line displays the tracked positions in the previous frames. These lines can help you compare different markers’ movements to determine if one of them is clearly off.
